This invention relates to a method of inhibiting virus and, more particularly, to a method of inhibiting viruses such as retroviruses with oxyand thio-substituted fatty acid analog substrates of myristoylating enzymes. These are substrates which are useful in the fatty acid acylation of peptides and proteins.
Fatty acid acylation of specific eukaryotic proteins is a well established process which can conveniently be divided into two categories. On the one hand, palmitate (C.sub.16) is linked to membrane proteins via ester or thioester linkage post-translationally, probably in the Golgi apparatus.
On the other hand, it is known that myristate (C.sub.14) becomes covalently bound to soluble and membrane proteins via amide linkage early in the protein biosynthetic pathway. In the N-myristoylated proteins, amino-terminal glycine residues are known to be the site of acylation.
A variety of viral and cellular proteins have been shown to be thus modified by the covalent attachment of myristate linked through an amide bound to glycine at their amino termini. An example of a most thoroughly studied myristoylated protein is the transforming protein (tyrosine kinase) of Rous sarcoma virus, p60.sup.v-src.
The myristoylation reaction can be represented as follows: ##STR1##
Further background information on the above protein fatty acid acylation can be had by reference to the following series of articles by scientists associated with the Washington University School of Medicine:
Towler and Glaser, Biochemistry 25, 878-84 (1986);
Towler and Glaser, Proc. Natl. Acad. Sci. USA 83, 2812-2816 (1986);
Towler et al., Proc. Natl. Acad. Sci. USA 84, 2708-2712 (1987);
Towler et al., J. Biol. Chem. 262, 1030-1036 (1987); and
Towler et al., Ann. Rev. Biochem. 57, 69-99 (1988).
Unique synthetic peptides having relatively short amino acid sequences which are useful as substrates of myristoylating enzymes are described in U.S. Pat. No. 4,740,588. Examples of such peptides are
Gly-Asn-Ala-Ala-Ala-Ala-Arg-Arg and PA0 Gly-Asn-Ala-Ala-Ser-Tyr-Arg-Arg.
Certain other unique synthetic peptides are inhibitors of myristoylating enzymes as described in U.S. Pat. No. 4,709,012.
The present invention is particularly concerned with a method of inhibiting retroviruses such as human immunodeficiency virus (HIV). As such, these fatty acid analog substrates have potential use for the treatment of acquired immune deficiency syndrome (AIDS) and AIDS-related complex (ARC).
Acquired immune deficiency syndrome, which only a few years ago was a medical curiosity, is now a serious disease. As a consequence, a great effort is being made to develop drugs and vaccines to combat AIDS. The AIDS virus, first identified in 1983, has been described by several names. It is the third known T-lymphocyte virus (HTLV-III) and has the capacity to replicate within cells of the immune system and thereby lead to a profound destruction of T4.sup.+ T-cells (or CD4.sup.+ cells). See, e.g., Gallo et al., Science 224, 500-503 (1984), and Popovic et al., Ibid., 497-500 (1984). This retrovirus has been known as lymphadenopathy-associated virus (LAV) or AIDS-related virus (ARV) and, most recently, as human immunodeficiency virus (HIV). Two distinct AIDS viruses, HIV-1 and HIV-2, have been described. HIV-1 is the virus originally identified in 1983 by Montagnier and co-workers at the Pasteur Institute in Paris [Ann. Virol. Inst. Pasteur 135 E, 119-134 (1984)], while HIV-2 was more recently isolated by Montagnier and his co-workers in 1986 [Nature 326, 662 (1987)]. As used herein HIV is meant to refer to these viruses in a generic sense.
Although the molecular biology of AIDS is beginning to be unraveled and defined, much more needs to be learned and understood about this disease. In the meantime, numerous approaches are being investigated in the search for potential anti-AIDS drugs and vaccines. Development of an AIDS vaccine is hampered by lack of understanding of mechanisms of protective immunity against HIV, the magnitude of genetic variation of the virus, and the lack of effective animal models for HIV infection. See, for example, Koff and Hoth, Science 241, 426-432 (1988).
The first drug to be approved by the U.S. Food and Drug Administration (FDA) for treatment of AIDS was Zidovudine, also known under its common name, azidothymidine (AZT). Chemically, this drug is 3'-azido-3'-deoxythymidine. This drug was originally selected as a potential weapon against AIDS because it was shown to inhibit replicaton of the virus in vitro. Such in vitro tests are useful and virtually the only practical method of initially screening and testing potential anti-AIDS drugs. A serious drawback of AZT, however, is its toxic side-effects. Thus, the search for better anti-AIDS drugs continues.